New technology and cost reductions in analytical methods are required for genomic and proteomic research projects. Microfluidic devices show promise as a solution for the analytical needs of these projects. The specific aim of this research is to develop an interferometric refractive index detection scheme for biological analytes in microfluidic devices. Interferometric refractive index detectors are highly sensitive and nonspecific. They will eliminate the need for development of fluorescent tags for proteins and carbohydrates. The fluidic and optical elements will be fabricated from polymers using soft lithography. The use of polymers will increase the flexibility of microanalytical systems and also lower their cost.